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1968 Cougar - stock 302. 1968 Mustang coupe - stock 302. 2012 Dodge Challenger R/T
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Discussion Starter #1
Why am I almost stalling and sputtering with acceleration from a stop?
I have almost finished a restoration project on my ‘68 coupe. It has a 302 with Edelbrock 1406 carb.
I finally got it running and driving last weekend and am super excited. Except, I have a sputtering issue.
Here is my problem. When my car is in park or neutral I have a very smooth idle at 800 RPM. When I put it into drive my idle drops a little but stays smooth. When I press the gas pedal to accelerate I get a sputtering and almost stalling sensation. If I can keep it running and get up to 30-40 mph the car will smooth out and drive efficiently.
Why is my car almost stalling/sputtering with initial acceleration from a stop?
FYI, All hoses are new, all carb gaskets Are new, And new fuel pump and filter. New distributor cap, but not new points.
 

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1968 Cougar - stock 302. 1968 Mustang coupe - stock 302. 2012 Dodge Challenger R/T
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Discussion Starter #3
I Completely agree it’s a fuel issue. I did replaced the spring in the accelerator pump and cleaned out the jets but didn’t replace them.
do you think if my floats aren’t set correctly that could be part of the issue?
 

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1968 Cougar - stock 302. 1968 Mustang coupe - stock 302. 2012 Dodge Challenger R/T
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Discussion Starter #4
Alright, so I unplugged my electric choke. Things were 80% better but still kinda bogged a little.
what exactly does an electric choke do and would this be a reason why my car wants to stall with acceleration from a stop?
 

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Alright, so I unplugged my electric choke. Things were 80% better but still kinda bogged a little.
what exactly does an electric choke do and would this be a reason why my car wants to stall with acceleration from a stop?
Electric choke closes throttle blade when cold. Over time the choke heats up and opens fully when warm. Make sure the plate it opening fully when warm. I think the sputtering you are experiencing is either accelerator pump or jetting. I put one size larger AP jets in my Holly to get the squirt right.

IIRC if you unplug the choke the blades stay closed causing you to run really rich. If your plates are closed and it runs better my guess is you are running way lean when the blade is open under normal driving conditions.
 

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Edelbrock 1406?
You said you replaced the accelerometer pump spring.
What about the pump diaphragm?
The spring is rarely the problem.

Yes the floats might need adjustment. When you take the top of the carb off to check the accelerator pump, check the float level too.
 

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1968 Cougar - stock 302. 1968 Mustang coupe - stock 302. 2012 Dodge Challenger R/T
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Discussion Starter #7
Yup, The diaphragm was replaced. It was part of the Edelbrock rebuild kit #1477. I did not replace the jets, just cleaned the ones I had. I’ll take a look at them again when I adjust the bowl floats.
Can you tighten the gets down too much?

so, wondering if there may be some fine dirt or particles in the old tank? I drained it and the gas was clean and smelled like gas. Nothing funny about it that made me worry, no sediment (nothing large that I could see), and actually thought to myself it looks like good gas. I still recycled it.
I just replaced the New fuel filter (1week old) with a brand new one I had on the shelf, and by golly it is better. Not perfect, still boys but no stalling. This is driving me crazy. Could the tank be dirty? Do I need to clean out the inside of my gas tank?
Ugg
 

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Just replacing the accelerator pump diaphragm or spring won't help, but the 1406 has 3 positions that affect pump stroke. Set the choke correctly, then set the timing correctly with the vacuum advance disconnected from the distributor and plugged at the carb end, reconnect that set the hot idle speed and idle mixture (800 seems a bit high), then set the accelerator pump stroke. That's what temporarily compensates for the lean condition momentarily caused by opening the throttle further.
 

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Discussion Starter #9
Thanks for the suggestions MFC66. I’ll take a look at doing that this weekend.
 
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